Those skilled in the arts of antenna arrays and beamformers know that antennas are transducers which transduce electromagnetic energy between unguided- and guided-wave forms. More particularly, the unguided form of electromagnetic energy is that propagating in “free space,” while guided electromagnetic energy follows a defined path established by a “transmission line” of some sort. Transmission lines include coaxial cables, rectangular and circular conductive waveguides, dielectric paths, and the like. Because of the delay associated with transmission of energy along transmission lines, they are sometimes known as delay lines. Antennas are totally reciprocal devices, which have the same beam characteristics in both transmission and reception modes. For historic reasons, the guided-wave port of an antenna is termed a “feed” port, regardless of whether the antenna operates in transmission or reception. The beam characteristics of an antenna are established, in part, by the size of the radiating portions of the antenna relative to the wavelength. Small antennas make for broad or nondirective beams, and large antennas make for small, narrow or directive beams. When more directivity (narrower beamwidth) is desired than can be achieved from a single antenna, several antennas may be grouped together into an “array” and fed together in a phase-controlled manner, to generate the beam characteristics of an antenna larger than that of any single antenna element. The structures which control the apportionment of power to (or from) the antenna elements are termed “beamformers,” and a beamformer includes a beam port and a plurality of element ports. In a transmit mode, the signal to be transmitted is applied to the beam port and is distributed by the beamformer to the various element ports. In the receive mode, the unguided electromagnetic signals received by the antenna elements and coupled in guided form to the element ports are combined to produce a beam signal at the beam port of the beamformer. A salient advantage of sophisticated beamformers is that they may include a plurality of beam ports, each of which distributes the electromagnetic energy in such a fashion that different beams may be generated simultaneously.
Radar systems often use multiple antenna beams for tracking of disparate targets, and sometimes for tracking single targets. One scheme for use of multiple beams involves monopulse techniques, in which angle tracking information is obtained from multiple beams, ideally with but a single transmitted pulse. Monopulse operation is accomplished by generating two, or more usually three, antenna beams, so that the simultaneously received echoes from the multiple beams can be compared. The usual monopulse beams are a sum (Σ) beam, and azimuth (Az) and elevation (El) difference (Δ) beams. Monopulse systems are described in many publications, as for example in U.S. Pat. No. 5,017,927 issued May 21, 1991 in the name of Agrawal et al. Agrawal et al. in one arrangement uses three separate beamformers, namely Σ, Az Δ, and El Δ beamformers, to generate the three different beams. These beamformers can be manifested in an array of a plurality of elevation Σ, Az Δ, and El Δ column beamformers which connect to the antenna elements, and an array of azimuth Σ, Az Δ, and El Δ row beamformers, which connect the E, Az Δ, and El Δ ports to the column beamformers.
FIG. 1 is a representation of a prior-art array antenna as described in the above-mentioned Agrawal et al. patent. As described therein in FIG. 1, radar system 10 includes an antenna array 12 including a set 14 of individual antennas or antenna elements 141, 142, 143, . . . 14N-2, 14N-1, and 124N arrayed in a column designated 161. Other columns 162, 163 . . . 16N are illustrated in a general manner as being located behind column 161, so as to form a two-dimensional rectangular array of antenna elements.
Each antenna element 141, 142 . . . 14N of columns 161, 162, . . . 16N of antenna array 12 of FIG. 1 is associated with a phase shifter 18. For example, elemental antenna 141 of column 161 is associated with a phase shifter 181. Similarly, each of the elemental antennas 142, 143 . . . 14N of column 161 are associated with a phase shifter 182, 183 . . . 18N. As also illustrated in FIG. 1, phase shifter 181 has an output transmission line (cable) 201 which, together with output cable 20N of phase shifter 18N of column 161, is connected to a sum-and-difference hybrid circuit 221. Each of cables 201 and 20N is connected to a separate input port (input) of hybrid circuit 221. It will be noted that phase shifters 181 and 18N are associated with elemental antennas 141 and 14N, the first and last (top and bottom) antenna elements of column 161. Similarly, the output of phase shifter 182 is coupled by way of a cable 202 to a second sum-and-difference hybrid splitter 222, together with the output from phase shifter 18N-1, coupled by way of a cable 20N-1. Phase shifter 182 is associated with antenna element 142, the second antenna element, and phase shifter 18N-1 is associated with penultimate antenna element 14N-2. A third sum-and-difference hybrid combining arrangement 223 receives inputs from the third antenna element 143 and its phase shifter 183 by way of cable 203, and from antepenultimate antenna element 14N-2 and its phase shifter 18N-2 by way of cable 20N-2, respectively. It can be seen that the outputs of the antenna elements of column 161 and their phase shifters are taken in pairs symmetrically disposed above and below the center of column 161, and the antenna outputs are combined in an array of sum-and-difference hybrids. The combination or array of sum-and-difference hybrids 22 associated with column 161 is designated 241.
Each of the other columns of FIG. 1, such as column 162, 163 . . . 16N, includes (not illustrated) its own column array of antenna elements 14 and phase shifters 18, each of which is associated with an antenna 14. Each of the other columns is also associated with an array 24 (not illustrated) of sum-and-difference hybrids 22. Only antenna array column 16N is illustrated in FIG. 1 as being connected by cables 20 to its associated sum-and-difference hybrid array 24N.
In the arrangement of FIG. 1, the sum output produced at the upper output of hybrid 221 of hybrid array 241, is coupled by way of a cable 261 to an input of a sum combiner or beamformer 301. Similarly, the upper or sum (Σ) outputs of sum-and-difference hybrids 222 and 223, and all the other hybrids (not illustrated) of hybrid array 241, are coupled by a cable 26 to sum combiner 301, which combines the sum signals, and which couples the combined sum signals to a single output cable 341. Similarly, the difference (Δ) output ports of sum-and-difference hybrids 221, 222, 223, . . . 22n/2 of hybrid array 241 of FIG. 1 are each connected by way of a transmission line 28 to separate inputs of a difference combiner or beamformer 321. Thus, the Δ (lower) output port of hybrid 221 is connected by way of a cable 281 to a first input of Δ combiner 321, the a output port of hybrid 222 is coupled by way of a cable 282 to a second input of Δ combiner 321, and the Δ output port of hybrid 223 is coupled by cable 283 to a third input of Δ combiner 321. All the other hybrids (not illustrated) of hybrid array 241 have their Δ output ports coupled to a Δ combiner 321 in a similar manner. Combiner 32′ combines the ′ signals and couples their sum to an output cable 36′.
Each of the other hybrid arrays 242 . . . 24M (only 24M illustrated) of FIG. 1 are connected to an associated pair of sum and difference combiners or beamformers in the same manner. The Mth hybrid array, namely 24M, is illustrated in FIG. 1, together with some of its cables 20, and also with some connection 26 to last column Σ combiner 30M. As so far described, all the columns 161 through 16M ultimately produce a sum signal from a column sum combiner 30 on a cable 34, and a difference signal from a column Δ combiner 32 on a cable 36. Thus, there are M cables 34, and M cables 36, one for each column 16. Elemental phase shifters 18 can be adjusted so that the input signals to column Σ combiners 30 add in-phase for a desired antenna beam pointing direction. Difference signals to column Δ combiner 32 will add in-phase only if cable pairs 26N and 28N are phase matched for all N, provided that the Σ and Δ combiners for each column have identical topologies. First cable 341 and last cable 34M from sum combiners 301 and 30M, respectively, are coupled to individual inputs of a sum-and-difference hybrid designated 381. The outputs from the second (302) and penultimate (30M-1) combiners (not illustrated) are coupled over cables 342 and 34N-1 to separate input ports of a second sum-and-difference hybrid 382. Similarly the third (303) and antepenultimate (30M-2) sum combiners 30 (not illustrated) have their outputs coupled by way of cables 343 and 34M-2, respectively, to a sum-and-difference hybrid 383. Other sum-and-difference hybrids (not illustrated) together with hybrids 381, 382, and 383, form an array 40M of sum-and-difference hybrids. Each hybrid of array 40M receives inputs from a pair of column sum combiners 30 associated with a pair of columns 16, the columns of which are symmetrically disposed to the left and right of the center of array 12.
The sum outputs of the hybrids of hybrid array 40M of FIG. 1 are each separately coupled by way of a cable 44 to a separate input of an azimuth sum combiner 48. For example, hybrid 381 has its Σ output connected by way of a cable 441 to an input of azimuth combiner 48, hybrid 382 has its Σ output connected by a cable 442 to another input of azimuth combiner 48, and hybrid 383 has its Σ output connected by way of a cable 443 to a third input of azimuth sum combiner 48. Azimuth sum combiner combines the Σ signals and produces the combined Σ signal on a cable 50 for application to a processing and display unit illustrated as 70. The Δ outputs of each of sum-and-difference hybrids 38 of hybrid array 40 of FIG. 1 are each separately coupled by way of a cable 46 to separate inputs of an azimuth Δ combiner 52. For example, the Δ output of hybrid 381 is connected by way of a cable 461 to an input of azimuth Δ combiner 52, the Δ output of hybrid 382 is connected to a second input of azimuth Δ combiner 52 by way of a cable 462, and the Δ output of hybrid 383 is connected by way of a cable 463 to yet another input of combiner 52. Combiner 52 combines the Δ signals and applies the combined signals over a cable 54 to processing and display unit 70 of radar unit 10. Another array 41 of sum-and-difference hybrids, each of which is designated as 42 in FIG. 1, is coupled to the array of M column Δ combiners 32 (only combiner 321 is illustrated), in much the same fashion that array 40 of hybrids 38 is coupled to an array of M sum combiners 30. For example, sum-and-difference hybrid 421 receives inputs by way of cables 361 and 36M from first and last column Δ combiners 321 and 32M (not illustrated). Sum-and-difference hybrid 422 is connected by way of cable 362 and 36M-1 to the second and penultimate column Δ combiner 32 (not illustrated), and hybrid 423 has its inputs connected by way of cables 363 and 36M-2 to the third and antepenultimate column Δ combiners 32. Other hybrids 42 of array 41 are connected to other pairs of combiners symmetrically disposed to the left and right about the center of array 12.
The sum outputs of each of sum-and-difference hybrids 42 of array 41 of FIG. 1 are coupled by way of separate cables 56 to separate inputs of an elevation Δ combiner 62. For example, hybrid 421 has its sum output connected by way of a cable 561 to a first input of combiner 62, and the sum outputs of hybrids 422 and 423 are connected by separate cables 562 and 563, respectively, to other inputs of elevation Δ combiner 62. Elevation Δ combiner 62 combines the column Δ signals to produce an elevation Δ signal on a cable 64 for application to processing and display unit 70. The difference (Δ) outputs of sum-and-difference hybrids 42 of hybrid array 41 of FIG. 1 are not used and are terminated. For example, the Δ output of hybrid 421 is coupled by way of cable 581 to a termination 601, and the Δ outputs of hybrids 422 and 423 are coupled by cables 582 and 583 to terminations 602 and 603, respectively.
A transmitter 72 associated with radar system 10 of FIG. 1 is coupled to processing and display unit 70 for timing the signals, for providing appropriate demodulation reference signals, and for other purposes. Also, a transmitter signal is applied to cable 50 of azimuth sum combiner 48, as suggested by dotted lines 74 within processing and display unit 70. The transmitter signals are coupled through azimuth combiner 48 and back through the arrays of hybrids and combiners, which in the context of transmission may act as splitters, to ultimately produce signals at antenna elements 14, which signals are phased in a manner appropriate for directing radiation in a particular direction.
The complexity of the beamforming arrangement of FIG. 1 is apparent. Additional complexity arises because of the amplitude weighting of the signals relative to each other in each column 16, and from column to column, in order to achieve the appropriate beam sidelobe levels for both elevation and azimuth beams. Even if phase shifters 18 are set correctly, assuming equal phase signals arriving at the phase shifters, cumulative phase errors through the combiners and hybrid arrays may adversely affect the performance. In this regard, it should be noted that the actual physical lengths of interconnecting cables such as 201, 202 . . . 20M must be nearly equal for wide bandwidth signals, and some cables such as 26N and 28N must have the same electrical length as well, even though the distances over which the signals must be carried may be less than the physical lengths This in turn tends to create a problem relating to excess cable lengths associated with the shorter paths, which excess cable lengths must be stored out of the way.
FIG. 2A is a simplified block diagram of a monopulse antenna array arrangement as described by Agrawal et al. Elements of FIG. 2A corresponding to those of FIG. 1 are designated by the same reference numerals. Array 12 of FIG. 2A includes a plurality of columns 2161, 2162, 2163 . . . 216M, corresponding generally to columns 16 of FIG. 1. Each column 216 of FIG. 2A includes a vertical array of N antenna elements 14, such as 141, 142, 143 . . . 14N-2, 14N-1, and 14N. Each antenna element 14 of each column 216 is associated with a transmit-receive processor or module (TR Proc). Thus, antenna element 141 of column 2161 is associated with a TR Proc 2181, elemental antenna 142 is associated with TR Proc 2182, and antenna 14N is associated with TR Proc 218N. Structurally, all TR Procs 218 are identical, although their adjustable portions (phase shifters, attenuators and/or switches) may be set differently.
As illustrated in FIG. 2A, each transmit-receive processor 218 has three outputs, designated 219, 220, and 221. For simplicity, the outputs of the TR processors are designated by the same reference numerals as that of the cables to which they are attached. Thus, outputs 2191, 2201 and 2211 of TR Proc 2181 of column 2161 are connected to cables 2191, 2201 and 2211, respectively. In a similar manner, the three outputs of TR Proc 2182 of column 2161 are connected to cables 2192, 2202 and 2212, respectively. The three outputs of TR Proc 218N of column 2161 are separately connected to cables 219N, 220N and 221N. As illustrated in FIG. 2A, the topmost or first TR processor 2181 of column 2162 is seen to be associated with output cables 2191, 2201, and 2211. In column 216M, TR processor 2181 is associated with cables 2191, 2201, and 2211. As in the case of FIG. 1, of course, all the columns 2162 . . . 216N are identical to column 2161.
The arrangement of FIG. 2A includes a Σ beamformer 230, an azimuth Δ beamformer 229, and an elevation Δ beamformer 231. All the cables 219 connected to TR processors 218 of array 12 are gathered in rows and columns in azimuth Δ beamformer 229. For example, all the cables 2191 from TR processors 2181 of all M columns 216 are separately connected to separate inputs located along a top row of beamformer 229. Similarly, all the cables 2192 from all the M TR processors 2182 of all columns 216 of array 12 are gathered and connected to the second row of inputs (not illustrated in FIG. 2A) of azimuth Δ beamformer 229.
FIG. 2B illustrates the connections of TR processors 218 of FIG. 2A to azimuth Δ beamformer 229 of FIG. 2A. In FIG. 2B, the connection face of beamformer 229 is seen in elevation view, with some of the inputs illustrated as dots. The connection face of beamformer 229 contains M×N input ports, one for each TR Proc 218, laid out as M columns and N rows. As can be seen, the upper row of inputs of beamformer 229 for columns 1, 2, 3 . . . M−2, M−1, M are each connected to a cable 2191. The second row of connections of beamformer 229 is to cables 2192, and the bottommost row of connections on the connection face of beamformer 229 receives cables 219N.
Sum beamformer 230 of FIG. 2A is connected to receive cables 220 in a same manner in which beamformer 229 is arranged to receive cables 219. That is, the topmost row of the connection face (not illustrated) of sum beamformer 230 is connected to cables 2201 from all M columns. The second row is connected to cables 2202, and so forth, until the lowermost row is connected to all cables 220N from all M columns. Elevation Δ beamformer 231 is similarly connected to receive cables 221 from all TR Procs 218 of array 12. Azimuth Δ beamformer 229 of FIG. 2A collects all the signals provided over cables 219 to form an azimuth difference signal which is coupled out over a cable 54. In the context of a radar system, cable 54 may be connected to a processor and display unit as described in conjunction with FIG. 1. Similarly, sum beamformer 230 and elevation difference beamformer 231 combine the signals from cables 220 and 221, respectively, to produce combined signals on cables 50 and 64, respectively.
FIG. 3 illustrates one possible arrangement for interconnecting the transmit-receive processors 218 of the arrangement of FIG. 2A, as set forth in the Agrawal et al. patent. In FIG. 3, elements corresponding to those of FIGS. 1 and 2A are designated by the same reference numerals. In FIG. 3, only column 216 and a portion of column 216M are illustrated. Each column of the array, including columns 2161 and 216M, is associated with three individual column beamformers designated 329, 330 and 331. In FIG. 3, azimuth Δ column beamformer 3291 is connected to receive cables 2191, and all other cables 2192, 219N of TR processors 2182-218N of column 216. Column 2161 sum beamformer 3301 receives inputs from cables 2201, 2202, 2202, . . . 220N-2, 220N-1, and 220N. Elevation Δ column beamformer 3311 is connected to receive cable 2211 from TR processor 2181 of column 2161 and cables 2212 . . . 221N from the remaining TR processors 218 of column 2161. Thus, column 2161, and all other columns 216 of array 12, is associated with three column beamformers, one for sum, one for azimuth Δ and the other for elevation Δ. Thus, cables 2201, 2202, 2203 . . . connect from TR processors 2181, 2182, 2183 of column 216M to sum column beamformer 330. Although not illustrated in FIG. 3, column M azimuth difference beamformer 329M is connected to cables 2191, 2192 . . . from the TR processors of column 216M, and column M elevation Δ beamformer 331M is connected to cables 2211, 2212 . . . 221N from the TR processors 218 of column 2161. Each column beamformer 3291-329M of FIG. 3 produces a signal on an output cable 3491-349M. All cables 3491 . . . 349M are connected to corresponding inputs of an array azimuth Δ beamformer 339, which combines the column signals to produce an array azimuth Δ signal on a cable 54. Similarly, elevation Δ column beamformers 3311 . . . 331M each produce a combined output on a corresponding cable 3511 . . . 351M, which are all connected to an array elevation Δ beamformer 341, which combines the signals to produce a combined elevation Δ signal on cable 64. Finally, each sum column beamformer 3301 . . . 330M combines its signals to produce a combined signal on a corresponding cable 3501 . . . 350M. All cables 3501 . . . 350M are connected to corresponding inputs of an array sum beamformer 340, which combines the signals to produce a combined sum signal on a cable 50. Array Σ beamformer 340 of FIG. 3, together with M associated column Σ beamformers 330, may be considered equivalent to sum beamformer 230 of FIG. 2A. Similarly, AZ Δ beamformer 229 of FIG. 2A corresponds to the combination of azimuth Δ beamformer 339 of FIG. 3 with a plurality equal to M of column AZ Δ beamformers 329. Elevation Δ beamformer 231 of FIG. 2A corresponds to the combination of elevation Δ beamformer 341 of FIG. 3 with all M of the column EL Δ beamformers 331.
More recent array antenna arrangements may generate more than three separate beams. In general, each beam is associated with a port of the beamformer. An overlap beamformer feeds at least some, and often most, elements of an antenna array with energy for multiple beams, and the number of beams may exceed three. Inexpensive and reliable interconnection(s) of the beamformer(s) with the antenna elements are desirable, but the topology of the connections tends to make conventional approaches tends to require a great deal of hand work and checking of connections against drawings. This hand work, in turn, tends to reduce the reliability of the connections, and increases the cost of the connections.
In FIG. 4, a plurality of rectangular or square planar dielectric circuit boards lie in a coplanar array 410. Each circuit board defines a broad upper side and a broad lower side, and each also defines four straight edges. The illustrated array 410 may be only a portion of a larger array made up of similar additional circuit boards. The illustrated circuit boards are designated 412a, 412b, 412c, 412d, 412f, and 412g. Other boards are illustrated in phantom, and ellipses indicate that the array may extend beyond the portion shown. The boards of FIG. 4 are supported by some underlying structure, illustrated as a support 490. An interstice, “gap” or interface lies between each board of array 410 and the next adjacent board on each side. Thus, a gap 414ab lies between mutually adjacent circuit boards 412a and 412b, a gap 414bc lies between mutually adjacent circuit boards 412b and 412c, a gap 414fg lies between mutually adjacent circuit boards 412f and 412g, a gap 416bd lies between mutually adjacent circuit boards 412b and 412d, a gap 416cf lies between mutually adjacent circuit boards 412c and 412f, and a gap 416bg lies between mutually adjacent circuit boards 412b and 412g. It will be noted that the gaps of set 414 of gaps have their directions (or axes) of elongation perpendicular to the directions of elongation of set 416 of gaps.
FIG. 5A is a plan or top view of a portion of an array of circuit boards similar to array 410 of FIG. 4, and corresponding elements are designated by like reference alphanumerics. For convenience, the array of FIG. 5A is designated 500. In addition to the circuit boards of set 500, FIG. 5A includes a set 510 of elevation Monolithic Microwave Integrated Circuits (MMICs) and a set 516 of azimuth (Az) MMICs.
The description herein includes relative placement or orientation words such as “top,” “bottom,” “up,” “down,” “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” as well as derivative terms such as “horizontally,” “downwardly,” and the like. These and other terms should be understood to refer to the orientation or position then being described, or illustrated in the drawing(s), and not to the orientation or position of the actual element(s) being described or illustrated. These terms are used for convenience in description and understanding, and do not require that the apparatus be constructed or operated in the described position or orientation. Similarly, terms concerning mechanical attachments, couplings, and the like, such as “connected,” “attached,” “mounted,” refer to relationships in which structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable and rigid attachments or relationships, unless expressly described otherwise.
In FIG. 5A, the elevation MMICs of set 510 “bridge” the gaps between the circuit boards of set 500 of boards, and make connection to the circuit boards on each side of the gap. Thus, a first MMIC designated 510bc1 bridges gap 414bc lying between circuit boards 412b and 412c. Similarly, a second MMIC designated 510bc2 also bridges gap 414bc lying between circuit boards 412b and 412c. A MMIC designated 510cz1 bridges gap 414cz lying between circuit boards 412c and 412z. Similarly, another MMIC designated 510cz2 also bridges gap 414cz lying between circuit boards 412c and 412z. A MMIC designated 510ab1 bridges gap 414ab lying between circuit boards 412a and 412b. Similarly, a MMIC designated 510ab2 also bridges gap 414ab lying between circuit boards 412a and 412b. A MMIC designated 510fΩ1 bridges gap 414fΩ lying between circuit boards 412f and 412Ω. Similarly, a MMIC designated 510 fΩ2 also bridges gap 414fΩ lying between circuit boards 412f and 412Ω. A MMIC designated 510fg1 bridges gap 414fg lying between circuit boards 412f and 412g. Similarly, a MMIC designated 510fg2 also bridges gap 414fg lying between circuit boards 412f and 412g. For completeness, a MMIC designated 510gh1 bridges gap 414gh lying between circuit boards 412g and 412h. Similarly, a MMIC designated 510gh2 also bridges gap 414gh lying between circuit boards 412g and 412h. 
It will be noted that the gaps of set 414 of gaps of FIG. 5A which are bridged by elevation MMICs of set 510 of MMICs are mutually parallel. That is, gaps 414ab, 414bc, 414cz, 414fg, 414gh, and 414fΩ are all parallel. The gaps of set 416 of gaps are orthogonal to the gaps of set 414, and are bridged by azimuth MMICs of a set 516 of azimuth MMICs. More particularly, gap 416bd of set 416 of gaps, lying between circuit boards 412b and 412d, is bridged by an azimuth MMIC 516bd, a gap 416cm lying between circuit boards 412c and 412m is bridged by a MMIC 516cm, gap 416ag lying between circuit boards 412a and 412g is bridged by a MMIC 516ag, and similarly a gap 416cf is bridged by a MMIC 516cf, a gap 416fΨ is bridged by a MMIC 516fΨ, and a gap 416gΦ, is bridged by a MMIC 416gΦ. It will be appreciated that the MMICs of sets 510 and 516 do not simply bridge their respective gaps, but that they also make connection by way of electrically conductive vias, pins, terminals, sockets, or other electrical conductors, to various conductors or transmission lines laid out on, or associated with the various circuit boards of set 412 of boards, as described hereinbelow.
The circuit boards of set 412 of FIG. 5A make contact not only with the various MMICs, but also make connections for beam ports and connections for antenna elements (or for TR modules associated with antenna elements, if provided). More specifically, various dots laid out on the circuit boards of FIG. 5A represent the locations of ports for connection to the antenna elements or their associated TR modules. In this context, a “port” may be in the form of an electrical connection associated with a transmission line. For example, circuit board 412f of FIG. 5A has one antenna element port designated “port 2.” Each circuit board of the embodiment illustrated in FIG. 5A has sixteen such ports, each of which is for connection (possibly by way of a TR module) to one antenna element of a subarray of sixteen antenna elements. The sixteen antenna element (or associated T/R module) connection ports of circuit board 412b of FIG. 5A are designated 1110, 1112, 1114, 1116, 1118, 1120, 1122, 1124, 1126, 11128, 1130, 1132, 1134, 1136, 1138, and 1140. Each circuit board of FIG. 5A has a single “beam” port at which the desired array antenna beam is generated, which ports are not illustrated in FIG. 5A.
FIG. 5B is a cross-section of one possible embodiment of the structure of FIG. 5A taken at section line 5b-5b. In FIG. 5B, the Az MMICs are shown as having rows of connection pins (seen as a single pin in this view) which makes contact with at least one conductor layer (not illustrated) of the circuit boards. More particularly, the connection pins of MMIC 516bd are designated 516bdP, the connection pins of MMIC 516bg are designated 516bgP, and the connection pins of MMIC 516gΦ are designated 516gΦP. These pins allow each MMIC to couple to each of the adjacent circuit boards, and ultimately allows the flow of signal among the circuit boards, across the gap lying between the circuit boards. While not expressly illustrated in FIG. 5B, the El MMICs of FIG. 5A similarly make contact with their underlying circuit boards by means of rows of connection pins.
FIG. 6A is a plan view of the upper surface of a single circuit board of FIG. 5A, showing the RF terminal and connection (pin, via, socket, or other electrical conductor) layout. For definiteness, the circuit board of FIG. 6A is designated as being board 412b. In FIG. 6A, the layout of connection locations for the azimuth MMIC 516bg is designated Az1 and contains connection locations A1, A2, A3, and A4, as well as connection locations A7, A8, and A9. The layout of connection locations for azimuth MMIC 516bd are designated Az2 and include connection locations A5, A6, as well as A10 and A11. It will be understood that the connection locations Az1 and Az2 are continuations of each other on opposite sides of the circuit board. The connection locations for the azimuth MMICs are laid out in two straight lines, with six locations (A1 through A6) in a first row and with five locations (A7 through A11) in a second row. Thus, a first Az MMIC can be mounted with some of its pins (if provided) in set Az1 of electrically conductive via, terminal, pin, or socket connections of FIG. 6A, and another similar Az MMIC can be mounted with the “remaining” pins in set Az2.
As mentioned, each circuit board has one “beam” port connection (electrically conductive pin, via, socket, terminal or the like) at which the desired receive beam is generated. The single beam port in FIG. 6A is the MMIC port connection designated A7 in pattern Az1. This beam port, and corresponding beam ports of all the circuit boards of FIG. 6A, may be coupled by signal paths to analog-to-digital converters and other or further beamforming processing, as known in the art.
FIG. 6B is a general bottom view representation of an azimuth MMIC module 616 which can be used in the arrangement of FIG. 5A, showing a pin (or other connection) layout compatible with the Az1 and Az2 portions of the circuit board of FIG. 6A, and also showing the location of the gap 616g which module 616 straddles. In FIG. 6B, the six connections or pins of a first row of Az module 616 are designated 616A1, 616A2, 616A3, 616A4, 616A5, and 616A6. Similarly, the five connections or pins in a second row are designated 616A7, 616A8, 616A9, 616A10, and 616A11. Pin, contact, via, terminal, or connection 616A7 is the beam port for one of the circuit boards associated with the azimuth module 616. In FIG. 6B, those connections designated with the “A” suffix with a numeral are spaced and arranged to mate with and make contact with connections having the corresponding A suffix and numeral of the circuit board of FIG. 6A. It should be remembered that the illustration of FIG. 6A is of the top of the board 412b, whereas the illustrations of FIGS. 6b and 6c are of the bottoms of MMICs, so there is an apparent “reversal” of the connection positions between the FIGURES. More particularly, connection 616A1 of integrated circuit 616 of FIG. 6B makes contact with connection A1 of circuit board 412b of FIG. 6A, connection 616A2 of integrated circuit 616 of FIG. 6B makes contact with connection A2 of circuit board 412b of FIG. 6A, connection 616A3 of integrated circuit 616 of FIG. 6B makes contact with connection A3 of circuit board 412b of FIG. 6A, and connection 616A4 of integrated circuit 616 of FIG. 6B makes contact with connection A4 of circuit board 412b of FIG. 6A. In addition, connection 616A5 of another integrated circuit similar to 616 of FIG. 6B makes contact with connection A5 of circuit board 412b of FIG. 6A, and connection 616A6 of this other integrated circuit makes contact with connection A6 of circuit board 412b of FIG. 6A. Further, connection 616A7 of integrated circuit 616 of FIG. 6B makes contact with connection A7 of circuit board 412b of FIG. 6A, connection 616A8 of integrated circuit 616 of FIG. 6B makes contact with connection A8 of circuit board 412b of FIG. 6A, and connection 616A9 of integrated circuit 616 of FIG. 6B makes contact with connection A9 of circuit board 412b of FIG. 6A. Further, connection 616A10 of an integrated circuit similar to 616 of FIG. 6B makes contact with connection A10 of circuit board 412b of FIG. 6A, and connection 616A11 of this other integrated circuit makes contact with connection A11 of circuit board 412b of FIG. 6A.
As described below, various connections, pins, vias or electrical conductors of Az MMIC 616 of FIG. 6B make connection to other functional structures of the system. More particularly, pins or connections 616A1, 616A2, 616A3, 616A4, 616A5, and 616A6 of MMIC 616 are for making azimuth-to-azimuth connections, connection or pin 616A7 is for connection to a beamforming port. Connections or pins 616A8, 616A9, 616A10, and 616A11 are for connection to elevation modules, for receipt of signals therefrom in reception mode.
Also illustrated on Azimuth IC 616 of FIG. 6B are blocks bearing designations corresponding to the functions (3:1; dual 2:1; 4:1, etc.) which are connected within the MMICs to the various connections or pins thereof. These are described in more detail below.
Also visible in FIG. 6A are the connection locations for the elevation MMICs corresponding to those making connection to circuit board 412b of FIG. 5A. More particularly, FIG. 6A shows a first elevation layout El1 of connections, which may be in the form of electrically conductive sockets, vias, terminals, pins, or other conductive paths. The connection layout or pattern of first elevation layout El1 includes a line of connections E1, E2, E3, and E4, together with a single connection E5 at one end of the pattern, and a further single connection E6 at the other end. The layout of these connections is selected to register with or match the connection or pin layout on one side of an elevation MMIC. The connections for the other side of an elevation MMIC are illustrated by a further layout E12 in FIG. 6A. Layout E12 includes a line of four connections E9, E10, E11, and E12, and two single connections adjacent the ends of the pattern. The two single connections are designated E7 and E8.
FIG. 6C is a plan view of the bottoms of a pair of elevation MMICs, designated as 510bc1 and 510bc2, corresponding to two side-by-side MMICs illustrated in FIG. 5A. In FIG. 6C, the connection or pin layouts of the two MMICs are identical. Thus, it is only necessary to describe one of the layouts to make the other clear. In MMIC 510bc1(B) of FIG. 6C a line of four connections (electrically conductive vias, sockets, terminals, pins, or other electrical conductors) 620E1, 620E2, 620E3, and 620E4 extends across an “upper” long side. Connector 620E1 is one end of a line of connectors including connectors 620E5, 620E7, and 620E9, which extend “vertically” to the “lower” long edge of MMIC 510bc1(B). Similarly, connector 620E4 is at an upper end of a line of connectors including connectors 620E6, 620E8, and 620E12, which line extends vertically to the lower long edge of the MMIC. As can be seen, connectors 620E1, 620E2, 620E3, 620E4, 620E5, and 620E6 lie on an upper side of gap 620g, and connectors 620E7, 620E8, 620E9, 620E10, and 620E11 lie on a lower side of the gap, indicated in FIG. 6C by line 620g. 
When MMIC 510bc1(B) of FIG. 6C is mounted across or straddling the gap between mutually adjacent circuit boards, such as gap 414bc of FIG. 5A, its connectors mate with the connectors of the circuit boards on either side of the gap. More particularly, connectors 620E1, 620E2, 620E3, 620E4, 620E5, and 620E6 of the MMIC mate with connectors E1, E2, E3, E4, E5, and E6, respectively, of pattern El1 of FIG. 6A. Similarly, the connectors 620E7, 620E8, 620E9, 620E10, 620E11, and 620E12 mate with the connectors of the next adjacent circuit board, which are illustrated in FIG. 6A as connectors E7, E8, E9, E10, E11, and E12 of pattern E12. It should be noted that FIG. 6C illustrates as blocks certain power dividers or combiners in MMIC 510bc1(B) which connect to various ones of the connectors associated with the MMIC. The connections of these blocks are described below.
As described below, various connectors of El MMIC 510bc1(B) of FIG. 6C make connection to other functional structures of the antenna beamforming system. More particularly, connections 620E1, 620E5, 620E7, and 620E9 of MMIC 510bc1(B) are for making connections to four of the associated antenna elements (or their T/R modules), connection or pin 620E4 is for connection to an azimuth MMIC, connections or pins 620E2, 620E3, 620E8, 620E10, 620E11, and 620E12 are for connection to other elevation MMIC modules, and connection or pin 620E6 is for a transmit connection.
It should be noted that the term “between” and other terms such as “parallel” have meanings in an electrical context which differ from their meanings in the field of mechanics or in ordinary parlance. More particularly, the term “between” in the context of signal or electrical flow relating to two separate devices, apparatuses or entities does not relate to physical location, but instead refers to the identities of the source and destination of the flow. Thus, flow of signal “between” A and B refers only to source and destination, and the signal flow itself may be by way of a path which is nowhere physically located between the locations of A and B. The term “between” can also define the end points of the electrical field extending between points of differing voltage or potential, and the electrical conductors making the connection need not necessarily lie physically between the terminals of the source. Similarly, the term “parallel” in an electrical context can mean, for digital signals, the simultaneous generation on separate signal or conductive paths of plural individual signals, which taken together constitute the entire signal. For the case of electrical current, the term “parallel” means that the flow of a current is divided to flow in a plurality of separated conductors, all of which are physically connected together at disparate, spatially separated locations, so that the current travels from one such location to the other by plural paths, which need not be physically parallel.
FIG. 7 illustrates receive-function internal connections among the ports and functional blocks of an Azimuth MMIC module such as 616 of FIG. 6B. The transmit function is not shown. In FIG. 7, representative Az MMIC 616 is connected to receive signals from the elevation modules at connections or pins 616A8, 616A9, 616A10, and 616A11. Signals from the elevation (El) modules are coupled between connections or pins 616A8 and 616A9 and the common ports 710c1 and 710c2 of a dual 1:3 splitter or coupler 710, and other elevation signals are coupled between connections or pins 616A10 and 616A11 and common or input ports 712c1 and 712c2 of a dual 3:1 splitter or coupler 712. These dual 1:3 couplers may produce two sets of three-way divided signal in receive operation. More particularly, dual 1:3 coupler 710 produces three pairs of independent signals, one pair of which is carried by way of a path 714 to an individual or input port pair of dual 2:1 coupler 716, another pair of which is carried by a path 718 to an individual or input port pair of 4:1 coupler 720, and a last pair of which is carried by a path 722 to an individual or input port pair of 3:1 coupler 724. Similarly, dual 1:3 coupler 712 produces three pairs of independent signals in receive operation, one pair of which is carried by way of a path 726 to individual input ports of a 3:1 coupler 728, another pair of which is carried by a path 730 to individual input ports of dual 2:1 coupler 716, and a last pair of which is carried by a path 732 to individual input ports of 4:1 coupler 720. A first common output port 716c1 of dual 2:1 coupler 716 is connected as an input to 3:1 coupler 728, and a second common output port 716c2 of dual 2:1 coupler 716 is coupled by way of a path 734 as an input to 3:1 coupler 724. The common port 728c of 3:1 coupler 728 is connected to MMIC connection or pin 616A6. The common port 724c of 3:1 coupler 724 is connected to MMIC connection or pin 616A3. The common port 720c of 4:1 coupler 720 is connected by a path 736 to MMIC connection or pin 616A4. Three-to-one (3:1) coupler 738 is coupled to receive signal from MMIC connections or pins 616A1, 616A2, and 616A5. The common port 738c of coupler 738 is connected to beamformer connection or pin 616A7.
FIG. 8 illustrates internal connections among the ports and functional blocks of an Elevation MMIC module such as 510bc1(B) of FIG. 6C. In FIG. 8, representative El MMIC 510bc1(B) is connected to receive antenna element signals at connections or pins 620E1, 620E5, 620E7, and 620E9. Signals are coupled between connection or pin 620E1 and a first common port 810c1 of a dual 3:1 coupler 810, and between connection or pin 620E5 and a second common port 810c2 of dual 3:1 coupler 810. Coupler 810 has three sets 810i1, 810i2, and 810i3 of individual or independent ports. A pair of signal paths 812 extends between the set or pair of individual ports 810i1 of coupler 810 and a pair of individual ports of a 3:1 coupler 814. A pair of signal paths 816 extends between the set or pair of individual ports 810i2 of dual 3:1 coupler 810 and a pair of independent ports of a 4:1 coupler 818. A pair of signal paths 820 extends between a set or pair of individual ports 810i3 of dual 3:1 coupler 810 and a set of independent ports of a dual 2:1 coupler 822. Similarly, signals are coupled between connection or pin 620E7 of FIG. 8 and a first common port 830c1 of a dual 3:1 coupler 830, and between connection or pin 620E9 and a second common port 830c2 of dual 3:1 coupler 830. Dual 3:1 coupler 830 has three sets of individual or independent ports 830i1, 830i2, and 830i3. A pair of signal paths 832 extends between the set or pair of individual ports 830i1 and a second pair of individual ports of dual 2:1 coupler 822. A pair of signal paths 834 extends between the set or pair of individual ports 830i2 of coupler 830 and a second pair of independent ports of 4:1 coupler 818. A pair of signal paths 836 extends between a set or pair of individual ports 830i3 of coupler 830 and a set of independent ports of a 3:1 coupler 840. One common port 822c1 of dual 2:1 coupler 822 is connected by a path 842 to an individual port of 3:1 coupler 840. Another common port 822c2 of dual 2:1 coupler 822 is connected by a path 844 to an individual port of 3:1 coupler 814. The common port 814c of 3:1 coupler 814 is connected by a path 846 to an individual port of 3:1 coupler 848. The common port 840c of 3:1 coupler 840 is connected by a path 850 to an individual port of “final” 3:1 coupler 848. The common port 818c of 4:1 coupler 818 is connected by a path 852 to a third individual port of “final” 3:1 coupler 848. The common port 848c of coupler 848 is connected to connection or pin 620E4.
The elevation MMIC arrangement of FIG. 8 as described provides for electrical connection to only four antenna elements. Each planar connection board, however, provides connection to sixteen antenna elements. The sixteen connections come about because there are four elevation MMIC modules associated with each planar beamformer circuit board, each making connection to four antenna elements. For example, planar beamformer circuit board 412b of FIG. 5A is associated with four elevation MMIC modules, namely modules 510ab1, 510ab2, 510bc1, and 510bc2.
FIG. 9 is a diagram illustrating some of the connections made to the azimuth MMIC modules, such as azimuth modules 516bd and 516ag of FIG. 5A, by electrically conductive traces defined in one or more layers (not separately illustrated) of circuit board 412b of FIG. 5A. Those skilled in the art will recognize that, in order to define proper transmission lines, one or more reference voltage points or ground planes must be defined among the various layers of the circuit board(s) in addition to the interconnection traces. Since these ground planes are well understood in the art, they are not expressly illustrated. In FIG. 9, elements corresponding to those of FIGS. 5a and 6a are designated by like reference alphanumerics. In FIG. 9, pin, via, socket, terminal or connection A1 of Azimuth pattern AZ1 is connected to connection A4 by a transmission-line path (path) 910, a path 912 connects connection A2 of AZ1 to connection A6 of pattern AZ2, and a path 914 connects connection A3 of AZ1 to connection A5 of AZ2. In FIG. 9, a path 915 connects a connection A9 of azimuth MMIC pattern AZ1 to connection E4 of elevation pattern EL1, and a path 916 connects connection A8 of AZ1 to a connection E4 of elevation pattern EL901. Also in FIG. 9, a path 918 connects connection A10 of azimuth pattern AZ2 to a connection E4 of elevation pattern EL903, and a path 920 connects connection A11 of azimuth pattern AZ2 to a connection E4 of elevation pattern EL902.
FIG. 10 is a diagram illustrating additional connections which may be made on one or more layers of printed-circuit board 412b. In FIG. 10, elements corresponding to those of FIG. 9 are designated by the same alphanumerics. A path 1010 extends from pin, via, socket, terminal, or other connection E10 of elevation pattern EL905 to connection E2 of elevation pattern EL902, a path 1012 extends from connection E11 of elevation pattern EL905 to connection E3 of elevation pattern EL902, and a path 1014 extends from connection E8 to connection E12 of elevation pattern EL905. A path 1020 extends from connection E10 of elevation pattern EL906 to connection E2 of elevation pattern EL903, a path 1022 extends from connection E11 of elevation pattern EL906 to connection E3 of elevation pattern EL903, and a path 1024 extends from connection E8 to connection E12 of elevation pattern EL906. A path 1030 extends from connection E10 of elevation pattern EL2 to connection E2 of elevation pattern EL1, a path 1032 extends from connection E11 of elevation pattern EL2 to connection E3 of elevation pattern EL901, and a path 1034 extends from connection E8 to connection E12 of elevation pattern EL2. Also, a path 1040 extends from pin, via, socket, terminal, or other connection E10 of elevation pattern EL904 to connection E2 of elevation pattern EL901, a path 1042 extends from connection E11 of elevation pattern EL904 to connection E3 of elevation pattern EL901, and a path 1044 extends from connection E8 to connection E12 of elevation pattern EL904.
FIG. 11 is a diagram illustrating additional connections which may be made on one or more layers of printed-circuit board 412b. In FIG. 11, elements corresponding to those of FIGS. 9 and 10 are designated by the same alphanumerics. In FIG. 11, pins, vias, sockets, terminals, or other connections 1110, 1112, 1114, 1116, 1118, 1120, 1122, 1124, 1126, 1128, 1130, 1132, 1134, 1136, 1138, and 1140 are for connecting the various antenna elements (or their associated T/R modules) associated with the beamformer connection board 412b to the elevation MMICs (not illustrated in FIG. 11). In other words, these connections are the antenna connections for the receive mode of operation. A signal path 1150 of FIG. 11 extends from connection E7 of elevation pattern EL905 to beamformer connection 1110, and a signal path 1152 extends from connection E9 to beamformer connection 1112. Signal paths 1154 and 1156 extend from connections E7 and E9 of elevation pattern EL906 to beamformer connections 1114 and 1116, respectively. Signal paths 1158 and 1160 extend from connections E7 and E9 of elevation pattern EL2 to beamformer connections 1118 and 1120, respectively. Signal paths 1162 and 1164 extend from connections E7 and E9 of elevation pattern EL904 to beamformer connections 1122 and 1124, respectively. Signal paths 1166 and 1168 extend from connections E1 and E5 of elevation pattern EL902 to beamformer connections 1126 and 1128, respectively. Signal paths 1170 and 1172 extend from connections E1 and E5 of elevation pattern EL903 to beamformer connections 1130 and 1132, respectively. Signal paths 1174 and 1176 extend from connections E1 and E5 of elevation pattern EL1 to beamformer connections 1134 and 1136, respectively. Signal paths 1178 and 1180 extend from connections E1 and E5 of elevation pattern EL901 to beamformer connections 1138 and 1140, respectively.
The beamforming performed in association with planar beamformer circuit board 412b of FIG. 11 produces a single beam upon reception, and the signal as received on this beam appears at port A7 of pattern Az1 at the lower right of the FIGURE. The signals received on the antenna beam defined by the receive beamformer 412B are connected to external utilization devices.
As so far described, the planar beamformer circuit boards have been destined for “central” locations of the array, which is to say locations at which adjacent beamformer circuit boards are coupled to all four edges. In these locations, signals are coupled to each beamformer from antenna elements of the array which are directly connected to the beamformer circuit board, and from antenna elements which are not directly connected to the beamformer circuit board. Thus, the received signals processed by each beamformer circuit board arise both from the antenna elements to which it is directly connected, and from antenna elements indirectly connected by way of other beamformer circuit boards. This results in an “overlap” of connectivity, in which each antenna element provides receive signal to more than one receive antenna beam. When N beamformer circuit boards are juxtaposed and connected in an array as described in conjunction with FIG. 5A, N individual beams can be generated. Each separate beam can be controlled, as known in the art, by adjusting the signal phases in the T/R modules.
Any antenna array has a finite size. Consequently, it has antenna elements which are at a “corner” or an “edge” of the array. Planar beamformers arranged in an array cannot support MMICs which would bridge a “gap” between a circuit board and the “missing” next adjacent circuit board. Thus, some beamformer circuit boards may be missing a mating beamformer circuit board at one edge in the case of an “edge” circuit board, and may be missing mating circuit boards along two edges in the case of a “corner” circuit board. Such beamformer circuit boards at the “edges” or “corners” of the beamformer array may require different circuit connections than those described for the case of “center” beamformer circuit boards. The different circuit connections are illustrated in FIG. 12. In FIG. 12, a “corner” connected board is designated 1212, and an “edge” board is designated 1214. The “free” edges of the array including boards 1212 and 1214 in FIG. 12 are designated F1 and F2, and other edges of boards 1212 and 1214 are connected to other portions of the array, as suggested by the outlines of the MMICs bridging gaps 1201, 1202, and 1203. In order to properly “terminate” connections which are not otherwise connected in an edge or corner circuit board, a “matched termination” as well known in the art is applied to the connection in question. The “matched termination” will often be simply a resistor connected to the connection or port and to reference ground, with the resistor value being related to the characteristic or surge impedance of the transmission line or of the element connected to the port. For example, connection or port 1110 of corner circuit board 1212 of FIG. 12 will ordinarily be connected by way of a transmission line (not illustrated) to the associated antenna element. The corner circuit board, however, does not have an associated antenna element to which port 1110 can be connected.
In FIG. 12, the locations of one end of each of the terminations, are indicated by dots. One set of four terminations is connected to terminals A5, A7, A10, and A11 of pattern AZ2 of board 1212. A set of six terminations is connected to terminals E7, E8, E9, E10, E11, and E12 of pattern EL905. A set of terminations is connected to terminals E7, E8, E9, E10, E11, and E12 of pattern EL906. A set of terminations is connected to terminals E7, E8, E9, E10, E11, and E12 of pattern EL2, and a set of terminations is connected to terminals E7, E8, E9, E10, E11, and E12 of pattern EL904. A similar set of terminations connects at the free edge F2 of board 1214 of FIG. 12. Those skilled in the art will know which other connections require such terminations.
FIG. 13 is a representation of two planar circuit boards 412b and 13412b, each including antenna ports. Some of the antenna ports of board 412b are designated 1110, 1112, . . . 1138, 1140. The antenna ports of board 412b are connected individually to antenna elements of a sixteen-element array or subarray 1310 by way of transmission lines designated together as 1314. Similarly, the antenna ports of board 13412b are connected individually to the antenna elements of a subarray 1312 by way of a plurality of transmission lines designated together as 1316.
Improved beamformers and interconnection arrangements therefor are desired.